Tap changing system



June 20, 1933-. BUCHHOLD. Er AL 1,914,907

TAP CHANGING SYSTEM Filed Dec. 24, 1951 2 Sheets-Sheet 1 June 1933. T. BUCHHOLD ET AL 1,914,907

TAP CHANGI NG SYSTEM Filed Dec. 24, 1951 2 Sheets-Sheet 2 IHIIIIDIIIIIIIIIIIIIIHIIIIII! illIIIllIllllmllllllllilllfl l illllll mum/M Patented June 20, 1933 TRUNITED STATES PATENT OFFICE THEODOR BUCHHOLD, OF MANNHEIM-NEUOSTHEIM, AND ERICK FLEISCHHAMMER, OF MANNHEIIYI, GER-MANY, ASSIGNORS TO AKTIENGESELLSCHAFT BROVJN BOVERI & CIEL, OF BADEN, SXVITZEBLAND, A JOINT-STOCK LOMPANY OF SWITZERLAND TAP CHANGING SYSTEM.

Application filed December 2 1, 1931, Serial No. 583,064, and in Germany December 8, 1930.

This invention relates to improvements in tap switches and in means for actuating such switches in a manner to vary the operations of an electrical apparatus withoutinterrupting the circuits involved and more particularly to a tap switching apparatus and system for controlling the operating energy supply to the motors of electrically driven vehicles.

Transformer tap switches are required to secure proper control of the voltage supplied to the traction motor of electrically driven vehicles. It is also required that such tap switcl as be so constructed as to be reliable and positive in operation and that only a very slight amount of arcing, if any, be permitted at the contacts. The dimensional limitations placed upon the electrical equipment of vehicles requires that all of the equipment including the tap switches be constructed as compactly as possible and that the operating mechanism for such switches be as small and light as possible consistent with positive operation of the switch.

It is therefore among the objects of the present invention to provide a system for crying the tap switch connections of electrical apparatus without interruption of the circuits connected with such apparatus.

Another object of the invention is to provide a switch. and tap switching system in which the tap connections may be altered under load without causing arcing at the switch.

Another object of the invention is to provide a system for switching the tap of electrical apparatus in which the circuit connections with. tap is disconnected only after the circuit connections with anothertap has been established.

Another object of the invention is to provide a system for changing the tap connections at electrical apparatus under load in which system means are provided for interrupting the circuits upon the occurrence of an over-load.

Another cbjcct'ot' the invention is to provide a switch for changing the tap connections of eleci'a'ieal' apparatus under load which switch will be more compact than prior switches for similar purposes.

Another object of the invention is to provide means for changing the tap connections of electrical apparatus under load in which the operating'forces are so balanced as to permit use of the lightest possible operating mechanism.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings in which Fig. 1 diagrammatically illustrates one embodiment of the present invention in which a tap switch having the fixed contacts thereof arranged in a circle is operated by the same means as are used to operate circuit interrupting switches which are also partially controlled by a safety device, and

Fig. 2 diagrammatically illustrates another embodiment of the invention in which a modified means for operating the rotatable contacts of the tap switch are shown.

-Referring more particularly'to the drawings by characters of reference, the reference numeral 3 designates a motor or rotary magnet controlled by mcans such as the main controller (not shown) of an electrically driven vehicle. The motor drives a bevel gear 41-. mounted on a shaft 5 which carries a disk 6 adapted tooperate a safety device to be described hereinafter. A bevel gear 7 engages with gear 4 and drives a shaft 8 on which are mounted a'bevel gear 9 and a gear 10. Geart) drives a bevel gear 12 which is mounted onfshaft 3 which shaft carries a bevel gear 14: operating circuit breaker switches to be described hereinbelow. The gear 10 drives a gear 16 mounted on a shaft 17 which carries contacts 18 and 19 rolling on the interior surface of a drum on which are arranged rows of contacts 21 and 22 and semicircular conductive bands or bus bars 23 and 24'. Although the fixed contacts and thebands of bus bars are shown in the drawing as arranged in different planes, it will be understood that, in practice, they may be arranged side by side and that the movable contacts bridging from one row of contacts to the adjacent bus bar may be also arranged side by side in the actual construction of the tap switch and are preferably formed as a single member. The movable contacts are spring pressed against the fixed contacts and the bus bar bands to secure a uniform contact pressure regardless of the position of such contacts.

The several contacts forming the semicircular rows 21 and 22 are connected with different points of a transformer winding 26 in an alternating arrangement so that the first one of each of the different rows of contacts are connected with adjacent taps 011 the v-winding and sue-"ceding contacts of the two rows are similarly connected to adjacent taps on the transformer winding. Each one of the bus bars and 24 is connected through a circuit interrupting switch with a traction motor 28 or other motor or electrical apparatus to which the supply of energy from the transformer winding 26 is to be controlled.

The gear 14 mounted upon and driven by shaft 13 engages with a 31 which drives a shaft 32 on which is mounted a cam 33. The cam 33 contacts with hell cranks 34 and 35 pivoted at 36 and 37 and forming the movable contacts of horn gap switches, the fixed contacts of which are designated at 34a and 35a respectively. which movable contacts connect the bus bars 23 and 24 through a reactance 38 with the motor or other apparatus to be operated as indicated at 28. Each of the horn gap switches is provided with a. blowout coil 41 and 42 respectively to aid in quenching the are upon opening of the switches and the switches are normally retained in the closed position by springs 44 and 45. The switches are adapted to interrupt the circuitbetween the transformer 26 and the motor 28 alternately upon the operation of the tap switch as will be understood from the explanation of the operation of the system which will be given below.

The switches 34. 34a and 35, 350 are also connected with and partially controlled by a safety device which operates to open the switches in response to pro-determined electrical conditions of the motor. A cam 51 is mounted in such manner as to be in contactwith the switch arms 34 and 35 and is secured on one end of a shaft 52 which carries a lever The lever 53 is normally held against alatch 54 by a spring 56. The latch is controlled by an electro-magnet 57 acting against a spring 58 upon energization of such magnet from a source of current 59. The position to which the latch 54 may be drawn by spring 58 is determined by a stop 60. Connection of source 59 with the coil of magnet 57 is controlled by a relay 61 having its operating coil connected through a cur rent transformer 62 with the motor circuit. delay 61 of such character as to be actuated to close its contacts upon the occurrence of a current in the circuit of the motor 28 above a predetermined limit to establish connection of the source of current 59 with the coil of magnet 57 which then trips latch 54 thereby releasing lever 53. Lever 53 is then rotated in a clockwise direction by spring 56 which causes shaft 52 and the cam 51 mounted thereon to be actuated, thereby causing opening of the circuit interrupting switches. Rotation of disk 6, however, causes pin 63 extending therefrom to contact with lever 53 thereby raising the lever 53 and causing its reengagement with latch 54. The operation of the safety device above described will be more fully setforth in the following description of the cycle of operations through which the various portions of the system must pass.

When the system is in the position shown in the drawings, the circuit between transformer winding 26 and the motor 28 is interrupted by the tap switch in the zero position, the horn gap switches 34 and 35 are closed and safety lever 52 rests on latch 54. If motor 3 is now energized from a suitable source of current controlled by the main controller of the vehicle, gears 4 and 7 will be rotated to drive shafts 5 and 8 which causes rotation of shafts 17 and 13 in a counterclockwise direction and thereby rotating shaft 32 in a clockwise direction. Clockwise movement of shaft 32 causes opening of the horn gap switches 35, 35a and 34, 34a respectively in the order named. Movable contact 19 is moved to position I before contact 18 reaches position II of the tap switch. Before contact 19, however, reaches position I, cam 33 will have permitted switch 34, 34a to close under the.

action of spring 44. When contacts 18 and 19 are therefore in position I, a circuit is completed from transformer winding 26 over contact 19, bus bar 23, blowout coil 41, switch 34 and 34a, the left hand section of reactance coil 38 and motor 28 to ground. Further movement of shafts 13 and 17 will cause switch 34, 34a to open and contact 19 will leave position I. The several gears and the cam 33 are so dimensioned that switch 34, 34a opens before contact 19 leaves position I, thus avoiding the necessity for interrupt ing the circuit at the row of contacts 21. Further rotation of shaft 17 causes movement of contact 19 from position I simultaneously with movement of contact 18 into position II. Cam 33 permits closing of switch 35, 35a under the action of spring 45 Mfore contact 18 comes into osition II. The switch 35, 35a being close upon the movement of contact 18 to position II. a circuit is completed from transformer winding 26 over contact 18, bus bar 24, switch 35, 35a and right hand section of reactance 38 to motor 28 and to ground. The above sequence of operations is repeated in the movement of contact 19 to position III and likewise upon movement of contact 18 to position IV and in all of the following positions of the tap switch until the movable contacts thereof reach position XII at which time the last tap of transformer winding 26 is connected with the motor 28 which is then supplied at the full voltage of the transformer windng 26.

During the above movement of shafts 13 and 17, haf't 5 has been rotated through the same angular distance duringthe movement of contacts 18 and 19 from position I into any of the other positions thereby causing pin 63 to move from the position shown in the drawings. Lever 53 is therefore released from pin 63 and rests only on latch 54. If the motor 28 is over loaded, relay 61will be energized from transformer 62 thereby closing the circuit of magnet 57 with the source of current 59 which magnet then trips latch 54 against the action of the spring 58. Lever 53 is then rotated in a clockwise direction by spring 56 to eng gement with stop 64 and rotates cam 51 which opens the switches 34, 34a and 35, 35a. As, soon as the overload has cleared, relay 61 is deenergized and interrupts the circuit to the coil of magnet 57 which permits spring 58 to return the latch into its original position against stop 60. Disk 6 is rotated upon the operation of motor 3 to return the tap switch into the zero position and pin 63 engages lever 53 which is thereby lifted and is permitted to drop against latch 54, due to the action of spring 56. Reversal of the direction of rotation of motor 3 returns contacts 18 and 19 to the zero position shown during the time disk 6 is being retiiirned to the position shown and is lifting lever 53. The system is then again entirely in the position shown in the drawings and is therefore in such. position that a new cycle of operation of the system may be initiated.

The embodiment of the present invention illustrated in Fig. 2 differs from that shown in Fig. 1 only in the means for operating the movable contacts 18 and 19 from the shaft 8 which has mounted thereon a gear 71. The gear engages with gears 72 and 73 mounted on shafts 74 and 75 which carry cranks 76 and 77. The cranks are adapted to engage in toothed substantially semicircular members 81 and 82 loosely mounted on a shaft 83 which membcrsform carriers for the movable contacts 18 and 19.

Assuming that the tap switch and the systom as a whole are in the Zero position as shown and that gear 71 is rotating in a counter clockwise direction it will be seen that c 'ank 76 will move in a clockwise direction thereby engaging the first notch of contact carrier 81 and will move contact 19 into position I. Crank 77 will move in a clockwise direction by the same amount of angular movement as the movement of crank 76 but will. merely come adjacent the first notch in carrier 82 during the time required to move contact 19 into position I. Continued rotation of shaft 8 and gear 71 will cause crank 77 to engage the first notch in contact carrier 82 which will move contact 18 into position II. During the above movement of crank 77, crank 76 will be rotated by a like amount which will bring the crank 76 adjacent the second notch in contact carrier 81 but not into engagement therewith. Further rotation of shaft 8 and gear 9 will rotate cam 33 thereby causing switch 34, 34a to be opened and will cause crank 76 to engage in the second notch of contact carrier 81 thus moving contact 19 from position I into position III. It Will be understood that the several gears and the cam 33 are so dimensioned that switch 34, 34a will open before contact 19 leaves position I thus avoiding the interruption of a circuit by the contacts of the top switch. During the above movement of crank 76, the crank 77 will be moved to adj acent the second notch in contact carrier 82 but not into engagement therewith. Further movement of shaft 8 and gear 71 will cause engagement of crank 77 with the second notch of contact carrier 82 and the movement of the contact carrier will cause movement of contact 18 from position III into position IV. Before such change of position of the contact 18, switch 35, 35a will be opened by the action of cam 33 thus preventing the necessity for the interruption of the circuit by the con- 23 and 24 are alternately opened and closed.

Each of the switches is opened before the movable contacts connecting the switch to the transformerwinding through the fixed contacts of the tap switch moves from one position to the other thus preventing interruption of the circuit to the motor by the tap switch.

- It will be seen that the resent invention provides a tap switch in w ich the movable contacts are relatively light and in which the entire switch requires only a very small space, both of which results are due to the particular construction and arrangement of the switch and the system and are of especial importance in electrically propelled vehicles such as railwaylocomotives in which both space and weight limitations are placed upon each portion of the electrical equipment thereof. The forces required for the operation of the switch are very small due to thefact that the movable contacts roll over the rows of fined contacts and over the bus bars of ti e tap switch under spring pressure and therefore practice ly without friction and because the movable contacts are oppositely arranged thereby preventing the occurrence of unbalanced forces. The arcing effects of the interruption of the circuit are limited to only two points in the system which points are so constructed that the contacts may be readily inspected and that damaged contacts may be removed without diliiculty. The safety device illustrated may be operated in response to any electrical condition in. the motor circuit and operates positively on the circuit interrupting switches. The operating mechanism for the entire system is very simple, light in weight and is eitremely positive in its operation.

Although but two embodiments of the present invention have been illustrated and described it will be apparent to those skilled in the art that various changes and modifications ma, be made therein without departing from the spirit of the invention or from the scope of the appended claims.

"The invention claimed is:

1. In a system for changing the tap connections of electrical apparatus under load, electrical apparatus supplied from the first ientioned apparatus, a. tap switch connected with the first mentioned apparatus, circuit breaking switches connecting said tap switch with the second said apparatus, asingle cam for alternately operating the said circuit breaking switches, and a single motor scans for operating said tap switch and said cam, the said means being operable to actuate said cam to operate said circuit breaking switches to their circuit opening position before operation of said tap switch to its circuit opening position.

2. In a. system for changing the tap connec tions oi": electrical apparatus under load, electrical apparatus supplied from the first mentioned apparatus, a tap switch connected with the first mentioned apparatus, circuit breaking switches connecting said tap switch with the second said apparatus, means for operating said tap switch and said circuit breaker at different times, and means responsive to abnormal electrical conditions. of the second said ap )aratus to cause circuit opening operation of aid circuit breaking switches.

3. In a system for changing the tap connections of electrical apparatus under load, electrical apparatus supplied from the first mentioned apparatus, a tap switch connected with the first mentioned apparatus, circuit breaking switches connecting said tap switch with the second said apparatus, a cam for operating said circuit breaking switches, means for operating said switch and said cam, said cam operating to open said circuit breaking switches before operation of said tap switch, and means responsive to abnormal electrical conditions of the second said apparatus to cause circuit opening operation of said circuit breaking switches, said cam and the last mentioned said means being connected to cooperate in controlling operation of said circuit breaking switches.

el. In a system for changing the tap connections of electrical apparatus under load, electrical apparatus supplied from the first mentioned apparatus, a tap switch connected with the first mentioned apparatus, circuit breaking switches connecting said tap switch with the second said apparatus, a cam for operating said circuit breaking switches, means for operating said switch and said cam, said cam operating to open said circuit breaking switches before operation of said tap switch, a second cam for operating said circuit breaking switches, and electromagnetic means energized in response to abnormal electrical conditions of the second said apparatus adapted to cause operation of the said second cam.

5. In a system for changing the tap connections of electrical apparatus under load, electrical apparatus supplied from the first mentioned apparatus, a tap switch connected with the first mentioned apparatus, circuit breaking switches connecting said tap switch with the second said apparatus, a cam for operating said circuit breaking switches, means for operating said switch and said cam, said cam operating to open said circuit breaking switches before operation of said tap switch, a second cam for operating said circuit breaking switches, electromagnetic means energized in response to abnormal electrical conditions of the second said apparatus and adapted to cause operation of the said second cam, and means adapted to restore the second said means to the non-operative position.

6. In a switch for changing the tap connections of electrical apparatus under load, a plurality of rows of fixed contacts connected with the apparatus, a bus bar adjacent each of said rows of contacts, movable contacts comprising anti-friction rollers for bridging the contacts of said rows and said bus bars, and means for causing simultaneous movement of said movable contacts to form alternate conductive connections of the contacts of said rows with said bus bars.

7. In a switch for changing the tap connections of electrical apparatus under load without interruption of circuit thereto, a plurality of rows of contacts arranged in a circle and connected with the apparatus, bus bars arranged adjacent said rows of contacts, contacts comprising anti-friction rollers movable into conductive connection with the con tacts of each row of said contacts with the adjacent one of said bus bars, and means for causing simultaneous movement of said movable contacts alternately into conductive position without interruption of the circuit.

8. In a switch for changing the tap conmotions of electrical apparatus under load without interruption of the circuit thereto, a plurality of rows of fixed contacts arranged in semi-circles opposite each other, bus bars arranged adjacent said rows of contacts, contacts comprising anti-friction rollers arranged opposite each other and movable to cause conductive connection of the contacts of each said row with the adjacent one of said bus bars, and means for causing simultaneous operation of said movable contacts to obtain conductive connection alternately between the contacts of each row of contacts and the bus bar adjacent thereto without in terruption of the circuit.

9. In a switch for changing the tap connections of electrical apparatus under load without interruption of the circuit thereto, a plurality of rows of contacts arranged in semi-circles opposite each other, bus bars ar- 5 ranged adjacent said rows of contacts, contacts comprising anti-friction rollers arranged opposite each other and movable to cause conductive connection of each contact of each row of said contacts with the adjacent one of said bus bars, said rollers being spring pressed against the contacts ofsaid rows and said bus bars, and means for simultaneously operating said movable contacts to obtain conductivle connection alternately between the contacts of each said row of confacts and the bus bar adjacent thereto without interruption of the circuit.

10. In a system of the character described, in combination, an electrical apparatus comprising a winding having a plurality of consecutively arranged taps, a tap switch comprising a plurality of rows of consecutively arranged fixed contacts, the successive contacts of the respective rows being connected i with alternate ones of said taps, cooperating movable contacts for each of said rows of fixed contacts, a circuit breaker connectable in series circuit with each said cooperating contact, means for alternately actuating said circuit breakers to circuit opening position, means for simultaneously actuating said cooperating contacts to alternately move from circuit closing connection with successive ones of said fixed contacts of the associated row, and means for causing simultaneous movement of the first and second said means to cause said circuit opening operations of said circuit breakers before movement of the asso ciated cooperating contacts from said circuit closing connection.

11. A tap changing under load system comprising, a tapped winding, a tap changing switch having a plurality of stationary contacts connected with said tapped winding and having two movable contact devices arranged to engage two of said stationary contacts connected with adjacent taps of said winding during transitory movement from one tap position to another and arranged to alternately engage only one of said stationary contacts when on tap positions, a circuit breaker serially connected with each of said two movable contact devices, a single cam for alternately operating said circuit breakers, and means operated by a single motor for actuating said two movable contact devices and said cam so that one of said circuit breakers is operated to its open position before the movable contact device serially connected therewith is operated to its open position.

In testimony whereof we have hereunto subscribed our names this 30th day of November, A. D. 1931.

THEODOR BUCHHOLD. ERICH FLEISCHHAMMER. 

